Pressure bonding and densification process for manufacturing low density core metal parts

Abstract

A novel method of forming low density core metal parts by pressure bonding face sheets to a porous foam metal core and simultaneously densifying the core is disclosed. In particular, low density core aluminum and aluminum alloy parts can be formed according to the method of the invention. The method of forming low density core metal parts generally comprises the steps of providing a porous, foam metal core and simultaneously pressure bonding first and second solid metal face sheets directly to opposite sides of the core and densifying the core by applying heat and uniaxial forge pressure to the first and second face sheets and to the core for a predetermined period of time. The method of the invention can therefore produce LDC parts having a predetermined shape and density. Furthermore, the LDC parts are less subject to interfacial oxidation and delamination than conventional LDC parts made by brazing.

That which is claimed: 
     
       1. A method for forming low density core metal parts comprising: providing a porous, foam metal core;   providing first and second solid metal face sheets having a particular shape, at least one of said face sheets being non-planar; and   simultaneously pressure bonding said first and second solid metal face sheets directly to opposite sides of the core and densifying the core to correspond generally to the shape of the face sheets by applying heat and uniaxial forge pressure to the first and second face sheets and the core for a period of time to produce a metal part having a low density, porous care.   
     
     
       2. The method according to claim 1 wherein said providing step comprises providing a porous foam core comprising a material selected from the group consisting of aluminum and aluminum alloys. 
     
     
       3. The method according to claim 1 wherein said step of simultaneously pressure bonding the face sheets to the core and densifying the core comprises applying heat at a temperature of between about 350° C. and 500° C. and pressure at up to about 1 ksi for between about 5 and 60 minutes. 
     
     
       4. The method according to claim 2 wherein said step of simultaneously pressure bonding the face sheets to the core and densifying the core comprises pressure bonding first and second face sheets formed of a material selected from the group consisting of aluminum and aluminum alloys. 
     
     
       5. The method according to claim 1 wherein the core has an original thickness prior to the application of heat and pressure, and wherein the step of simultaneously pressure bonding the face sheets to the core and densifying the core comprises densifying the core to no more than about 50% of the original thickness. 
     
     
       6. The method according to claim 1 wherein said providing step comprises providing a core having a porosity of between about 75 and 95 percent. 
     
     
       7. The method according to claim 6 wherein the step of simultaneously pressure bonding the face sheets to the core and densifying the core comprises densifying the core to a porosity of between about 30 and 50 percent. 
     
     
       8. The method according to claim 1 further comprising the step of removing oxides and other contaminants from the first and second face sheets prior to pressure bonding the face sheets to the core. 
     
     
       9. The method according to claim 1 further comprising the step of removing oxides and other impurities from the core prior to pressure bonding the face sheets to the core. 
     
     
       10. The method according to claim 1 wherein said step of simultaneously pressure bonding the face sheets to the core and densifying the core comprises pressure bonding the face sheets to the core and densifying the core in a hot press evacuated to a pressure of less than about 10 -6  torr. 
     
     
       11. The method according to claim 1 wherein said step of simultaneously pressure bonding the face sheets to the core and densifying the core comprises pressure bonding the face sheets to the core and densifying the core in a hot press in an inert environment. 
     
     
       12. The method according to claim 1 wherein said step of simultaneously pressure bonding the face sheets to the core and densifying the core comprises vacuum bagging the face sheets and the core in a steel envelope, placing the steel envelope in a hot forge, and simultaneously pressure bonding the face sheets to the core and densifying the core in the hot forge. 
     
     
       13. The method according to claim 1 wherein said step of simultaneously pressure bonding the face sheets to the core and densifying the core comprises providing a forming die having a shape and pressure bonding face sheets which correspond generally to the shape of the forming die to the core to form a low density core part having a shape that corresponds generally to the shape of the forming die. 
     
     
       14. A method for forming low density core aluminum or aluminum alloy parts comprising: providing first and second solid metal face sheets having a shape such that at least one of said face sheets is non-planar and providing a porous, foam core having an original thickness and a shape which corresponds generally to the shape of the face sheets, the core and face sheets comprising a material selected from the group consisting of aluminum and aluminum alloys;   removing oxides and other impurities from the face sheets and the core to thereby facilitate bonding therebetween; and   simultaneously pressure bonding first and second face sheets directly to opposite sides of the core and densifying the core to no more than about 50%, of the original thickness to, produce an aluminum or aluminum alloy part having a low density, porous core by applying heat at a temperature of between 350° C. and 500° C. and uniaxial forge pressure up to about 1 ksi to the first and second face sheets and to the core for between about 5 and 60 minutes.